Germany, which has lately united 80 million Germans, has submitted certain neighboring countries to her supremacy and gained military strength in many aspects, and thus has become, as clearly can be seen, a dangerous rival to principal imperialistic powers in Europe – England and France. That is why they declared war on Germany on a pretext of fulfilling the obligations given to Poland. It is now clearer than ever, how remote the real aims of the cabinets in these countries were from the interests of defending the now disintegrated Poland or Czechoslovakia.

Events arising out of the Polish‑German War has revealed the internal insolvency and obvious impotence of the Polish state. Polish ruling circles have suffered bankruptcy. . . . Warsaw as the capital of the Polish state no longer exists. No one knows the whereabouts of the Polish Government. The population of Poland have been abandoned by their ill‑starred leaders to their fate. The Polish state and its government have virtually ceased to exist. In view of this‑state of affairs, treaties concluded between the Soviet Union and Poland have ceased to operate. A situation has arisen in Poland which demands of the Soviet‑Government especial concern for the security of its state. Poland has become a fertile field for any accidental and unexpected contingency that may create a menace to the Soviet Union. . . . Nor can it be demanded of the Soviet Government that it remain indifferent to the fate of its blood brothers, the Ukrainians and Byelorussians White Russians inhabiting Poland, who even formerly were without rights and who now have been abandoned entirely to their fate. The Soviet Government deems it its sacred duty to extend the hand of assistance to its brother Ukrainians and brother Byelorussians inhabiting Poland.

The joint invasion of Poland was celebrated with a parade by the Wehrmacht and the Red Army in Brest Litovsk.

Kitchen, Martin (1990). A World in Flames: A Short History of the Second World War. Longman. p. 74. ISBN 0582034086.

The generals of the two invading armies went over the details of the prearranged line that would mark the two zones of conquest for Germany and Soviet Russia, subsequently to be rearranged one more time in Moscow. The military parade that followed was recorded by Nazi cameras and celebrated in the German newsreel: German and Soviet generals cheek by jowl n military homage to each other's armies and victories.